The field of the invention is butterfly-type valves, more particularly a butterfly-type valve for controlling liquid chemical application from aircraft. The valve in its open position directs fluid to a spray outlet leading to a set of spray nozzles, and in its closed position directs the fluid to a recirculating outlet leading back to a reservoir thus keeping the fluid mixed and ready for instant delivery to the spray nozzles when desired.
A prior art search was made in Class 137, sub classes 625.12, 625.13, 630.17, 614.18, 625.44 and Class 251, sub class 305. U.S. Pat. No. 3,956,073, Carbone et al, discloses a butterfly-type valve with plural outlets but without a shield to close a passage. U.S. Pat. No. 3,078,070, Cooper, shows a butterfly-type valve which similarly can be applied to plural paths as in FIG. 5, but does not have a shield to close off one passage, as the present invention. U.S. Pat. No. 3,147,773, Matthews et al, discloses in FIG. 2 a pair of coordinated butterfly valves that close one passage when they open another, but is not like the present invention.
The type of agriculture chemical spray valve now in use throughout the industry is a ball-type valve which is rotated in a valve body to direct the fluid either to the spray outlet or to the recirculating outlet. The valve now in use also has an aspirator consisting of a passage from the spray outlet to a venturi section in the recirculating outlet which creates a suction whenever the fluid is being recirculated. This draws the fluid from the spray outlet thus facilitating prompt shutoff and eliminating dripping. This aspirator feature is also included in the butterfly-type valve of this invention. The fluid for spraying consists of an active chemical diluted with water and a wettable powder which is usually a fine-grained clay. The clay is a disirable ingredient for dilution but causes friction between the ball and the valve seals due to the clay's abrasiveness. This friction is sufficient to require a force of about 40 pounds (18 kilograms) to operate the valve after it has been in service a short time. A pilot of the aerial application aircraft at the end of a pass has to close the valve, place his plane in a climbing attitude, simultaneously execute a tight 180.degree. turn, and then reopen the valve as he begins the next pass. When the valve requires a force of 40 pounds (18 kilograms) to operate, it can interfere with making such a maneuver efficiently, thus creating a problem. The problem is solved by this invention which markedly reduces the force needed to operate the valve. It is also important that the valve operate easily and quickly to insure coverage of the entire crop being sprayed and avoid a problem that would occur if the fluid reached other crops beyond either end of a pass on which the fluid is not wanted. Importance of avoiding overspray is seen in a list of chemicals used; not only pesticides, fungicides, and fertilizers but also herbicides to control weeds and defoliants to aid harvesting cotton and potatoes.